...and now we're running way too lean...

Well, I rebuilt the carbs. Made sure there were no vacuum leaks. Got myself a nice mercury free manometer carb sync set. If I set my pilot mixture screws in to 2.5 turns out, the bike won't even dream about starting. If I set them out to 5 full turns, I can start it and even get it to idle relatively steady. I could not sync them with the carb sync with the PM screws at 2.5 turns, as the bike would not start at that setting. Also, when turning them in after starting the bike, the cylinders will not fire with them turned in more than 4-5 full turns out from seated. The washers/o-rings I have in the carbs now are ones I ordered from Chacal. At 6.5 full turns out, I am able to ride it to work and back, 5 blocks. It still misses quite a bit, has trouble starting even with full choke, and backfires a little. All of the plugs are showing lean. What are my options here? I have put the #120 main jets back in, and have new #40 pilot jets. I am considering increasing the size of the pilot jets, but figured I should check with you guys first to see if there may be another issue I am not seeing. Thanks in advance for the help.

 

you shouldn't have to change the jet sizes from stock, unless you have fitted pod filters.
you could have the jets reversed. it should be main jet (large) pilot jet (small) bolt hole.

 

I only changed the main and pilot fuel jets in the bottom of the carbs. I did not change the air jets in the tops of the carb under the hats and piston diaphragm. Those are stock at #225 main air jet and #80 pilot air jet. I have checked the order of those as well to make sure they were inserted properly. I know the Haynes manual has them reversed in one of the exploded diagrams. As the bike sits right now, all the fuel and main jets are stock sizes. I figured it would be easy enough to sync and tune at stock settings, but it won't even idle at 2.5 turns out on pilot mixture screws. Just to make sure, the order from bottom to top on pilot mixture screws is oring, washer, spring, screw, correct? That is how they are installed in all four carbs.

 

Yes, that's the right order, try running on "prime"

 

I actually rode it around for a day on prime, ran about the same as it does in on position. I can't find any vacuum leaks at all on the carbs. Before I rebuilt them, I had some serious leaks on the throttle shaft. I actually had the exact opposite problem. I was fouling plugs within 3 miles of riding. I would think that with the vacuum leaks the carbs would have been lean, but nope. Now that I've replaced everything on the carbs (except the enrichment circuits, but I did take them apart and clean the hell out of them) and now I can't get rid of a lean condition. I have the carbs synced with the pilot mixture screws out about 6.5 turns out. I'm not sure whether or not the mixture screw settings affect the sync process or not, but that's the only setting I could get the bike to idle at without revving up instantly to very high RPMs, and the RPMs staying high when I turned the throttle at all. If I set the RPMs at 1050 with the bike running like that, it would not stay running at all, and would immediately die. The 6.5 turns out setting was the setting I could get the bike to idle without dying, and without revving up instantly. I realize that this is not an acceptable place for the screws to be set, which is why I'm going over options to fix the problem. I was thinking if I put a size or two larger on the pilot fuel jet, it might make up the difference and I could set the mixture screws closer to 3 turns out. I'd definitely be willing to try other options first though, as larger jets is more of a masking of the problem than a fixing of it.

 

Hi Shad - just noticed your xs850 - my one and only brand new bike - never should have sold it! I loved it.

Mixture settings do effect the sync. It's an iterative process, tune sync repeat.

I'm at a loss on the lean condition - are your float levels good?

 

Did you bench-sync the carbs?

 

I did bench sync the carbs. I have the float levels set just right on all four carbs. I tried to tune it a bit more today, but still no luck. Won't fire at all on 2 and 3 with the mixture screws set at spec. Is there any argument against increasing the size of my pilot fuel jets a step or two? I'll keep trying to tune it a bit more each day in the meantime. ... I just bought that XS850 recently for 50 bucks. I put a ton of work into it today and yesterday, rebuilt the clutch, did some repairs to the shift selector, cleaned up alot on it. Got the clutch back together, alternator on, was just sitting down to put the exhaust back on the bike when I noticed a washer I had forgotten to re-install. So, it looks like another tear down of the left side is on the slate for tomorrow.

 

6.5 Turns Out?
You might as well take them right out of the holes so you don't lose them.

At 6.5 Turns Out ... you were well past "Wide Open" ... 2 Turns or more.

 

that's what I thought as well. I don't know what else to do though. Anything less than 6.5 turns and I cannot even idle the bike without the throttle "hanging" at whatever RPM i turn it up to. Less than 5 turns out and the bike won't even start. Think larger pilot fuel jets, or maybe larger air jets? I'd like to fix this problem, I just don't know what to try next, I'm all out of ideas.

 

I'm sure that "Hanging" situation is a clue. Get into that with a little more detail.
Did you test for Air Leaks?
Are you positive that your Carbs have the right Jets?

Do you have any Jets to experiment with?

 

I am positive that the main fuel jets are #120, and the pilot fuel jets are #40. The main air jets are #225, and the pilot air jets are #80. I have sprayed all over the carbs and boots with water, and again with starting fluid, and did not notice any air leaks. I spent another 1.5 hours today trying to get the bike to run at all with the mixture screws turned out 2.5-3 turns, but the bike won't even start at that setting. I synced it again with each adjustment I made to the mixture screws. It seems like 6 turns out is the furthest in I can turn them before it stops firing in each cylinder. The "hanging" and racing throttle can be stopped by turning the main idle screw out, but this drops the RPMs at idle too low for the bike to stay running and it immediately dies. The only other jets I have to experiment with are #116 main fuel jets I had bought when I did the rebuild. I put the #120s back in to try and at least get it to run with stock settings, which I can't seem to do.

 

The Bike "Runs" ... Idles and gets set-up to accelerate by the Fuel Supplied to the Combustion Chambers by:
Pilot FUEL Jet in the Float Bowl.

Get a Syringe.

Insert it in the Pilot AIR Jet. Beneath the Diaphragm.
Squeeze the Air out of it before inserting it tightly in the Pilot AIR Jet and see if there is any blockage in the Passages.
The Test is to see if Gas can be sucked-up through the passage.

Plug the Pilot Mixture Screw Hole off if the Screw is out.

 

Sounds like a good test. Should I leave the float bowls full of fuel when I do this? Also, would it be odd that all of the jets were blocked?

 

Odd?
No way.
I had to pull my Carbs, last season, and clean-out crud I picked-up in bad gas.
It was so fine it got through an Inline Filter.

If you have Beenie Screens ... they can clog and keep the Fuel Level too low for the bike to run; too!